I checked your forecast and compared it with a pollen count for the same day. Why were they strikingly different?

There could be many reasons why our forecast ends up different than a pollen count reported for the same period. Let's take an example that today's pollen count reported on a local radio station as high, is different than Allergy Alert's forecast of a 4.5 (bottom of the medium range). Here are just a few:

The pollen count reported on the radio as today's count is actually the 24 hours previous to some hour today, at best. Remember that pollen counts represent pollen concentrations in the air in the very recent past. To magnify the difference, many times pollen counts are reported late, or treated as current when they were actually taken a few days ago. Occasionally you may have noticed a pollen count staying exactly the same a few days in a row. It is highly unlikely that the pollen concentration was this constant; it is more likely that the report was repeated due to lack of new information from that pollen counting station.

The pollen count reported on the radio as today's count is actually covering numerous days in the recent past. For instance, on Mondays, many pollen counting stations report a count which covers the period of Friday through Monday, since no personnel were at the office to take down a sample from their rooftop sampler over the weekend. This count represents more of an "average" than any true daily pollen events, but is very likely reported as "Monday's count." These longer sampling periods can be found throughout any part of the week, too, due to lack of availability of the personnel needed to retrieve and analyze the samples.

The pollen count reported on the radio is using a non-uniform scale. Some pollen counting stations determine their own low, medium, and high levels, meaning that a count we would consider in the medium range may be listed as in the high range by that particular station. Unfortunately, there aren't any guaranteed reporting standards that a pollen counting station must follow. The American Academy of Allergy, Asthma & Immunology (AAAAI) has a set standard, but not all stations follow it.

The pollen forecast takes into account forecasted weather. As we all know when our carefully planned picnics get rained out, that weather forecasts are not perfect. If the actual weather does not come out as forecasted, it is very likely that our pollen forecasts will not match an actual pollen count taken in that area for the same time period.